Concentration of ores by flotation



GUY E. SHERIDAN AND GEORGE G. GRISWOLD, JR, OF BUTTE, MONTANA.

CONCENTRATION OF ORES BY FLOTATION.

Ho Drawing.

T 0 all whom it may concern:

Be it known that we, GUY E. SHE IDAN Flotation; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to the concentration d of ores by flotation, and more particularly to the differential flotation of mixed sulfide ores. The invention has for its object the provision of an improved method of concentrating mixed or complex sulfide ores by differential flotation. More particularly, the invention aims to provide an improved method of concentrating by differential flotation a mixed or complex sulfide ore con taining galena associated with other metallic sulfides, such as Zinc, iron, copper and silver sulfides.

Complex or mixed sulfide ores, such, for example, as an ore carrying sulfides of lead,

zinc, copper and'iron, have offered many difficulties to treatment by gravity concentration as well as by flotation, and in the case of many ores of this type, it has heretofore been practically impossible to make an economic separation of the various metalliferous constituents of the ore from one another. Our present invention contemplates an improved method of treating a complex or mixed sulfide ore containing galena associated with zinc or iron sulfide, or both, whereby the galenamay be separated by flotation from the ore, and the resulting tail-- ings of this flotation treatment may then, if desired, be subjected to a further flotation treatment for the recovery of the zinc therefrom. Any copper or silver sulfide present in the ore will follow the galena and will be recovered in the lead concentrate. In general, the invention involves treating the mixed or complex sulfide ore, reduced to a flotatable size. with a cyanide and an alkaline salt. We. have also found that the selective or diflerential flotation of the lead sulfide is facilitated by-heating the ore pulp during the treatment with the cyanide and alkaline salt. In many instances, particularly in the treatment of an ore containing zinc sulfide, improved results are obtained Specification of Letters Patent.

Patented July 4, 1922.

Application filed January 13, 1921. Serial No. 437,030.

bythe addition of zinc sulfate to the ore pulp.

In carrying out the invention, the ore, in a finely divided condition, reduced to the condition of an ore pulp containing from 30% to 80% more or less by weight of water, is treated with a cyanide and an alkaline salt. An alkali, an alkali earth or a metallic cyanide may be employed in practicing the invention, and the alkaline salt may advantageously be an alkali carbonate or bicarbonate, such, for example, as sodium carbonate or sodium bicarbonate. In actual practice, we have found that satisfactory results are obtained by using-from a fraction of a pound to four pounds of an appropriate cyanide per ton of ore and from one to ten pounds of an alkaline salt, such as sodium carbonate or sodium bicarbonate, per ton of ore. The cyanide and, alkaline salt are thoroughly mixed with the ore pulp in any appropriate mixing apparatus, and We prefer to carry out this mixing operation as a preliminary step to the flotation treatment proper. To this end, we prefer to thoroughly incorporate the cyanide and alkaline salt with the ore pulp in an external mixing or agitation tank, whereupon the ore pulp, further diluted with Water if necessary, or desirable, is introduced into a flotation cell or apparatus of any of the Well known types. The; flotation treatment is conducted in the presence of an appropriate frothing agent,

, such as Oll.

We find that the effectiveness of the treatment of the ore with a cyanide and alkaline salt is enhanced by heating the ore pulp. For this purpose. the ore pulp may be heated as high as 212 F., although We find a temperature of 120 to 180 F. very satisfactory. The treatment of the ore pulp with the cyanide and alkaline salt, preferably heated as just described, may continue for a period of time ranging from two minutes to several hours, depending upon the character of the ore. The ore pulp isthen preferably diluted with cold Water until the temperature of the pulp is approximately 130 F.; a small amount of an appropriate frothing agent, such as oil, is then added to the ore pulp, and the ore pulp is then subjected to a flotation treatment for the removal of the lead sulfide.

In the case of a complex or mixed sulfide ore containing zinc sulfide, we find it of adup to four pounds of zinc sulfate, or equivalent salt. per ton of ore, during the pretreatment of the ore pulp with the cyanide and alkaline salt as aforementioned- In the Y may be obtained by subjecting the tailings from the second flotation treatment to a further flotation treatment in the presence of an additional amount of an appropriate frothing agent.

The practice of the invention will be further illustrated by the following examples:

1. A charge of ore, ground through 65 mesh, was agitated in a tank with equal amount of water (by weight) for one hour 1 at a temperature of 160 R, with 10 pounds of sodium carbonate and 1 pound of sodium cyanide per ton of ore. The ore pulp was then transferred to a flotation machine, diluted to 80% of water, and oil added. A froth formed which carried the greater portion of the lead sulfide in the ore. The results of this run are indicated in the following tabulation:

2. A charge of ore, ground through 05 mesh, was agltated in a flotation cell with an equal weight of water for three minutes at a temperature of 160 1 with 5 pounds of sodium bicarbonate, 2 pounds of zinc sulfate and 1 pound of sodium cyanide (added either as a powder or in solution) per ton of dry ore. The pulp was then diluted to 80% of water, and an appropriate oil added. After the removal of the lead concentrate by a flotation treatment, 2 pounds of sodium hydrate (per ton of dry ore) was added tothe remaining ore pulp, together with an additional amount of oil, and the ore pulp was then subjected to a second flotation treatment and a zinc concentrate obtained from Xthe resulting overflow froth. The results (if this run are tabulated below:

The zinc middling set forth in the preceding tabulation was obtained by subjecting the first, or rougher, zinc concentrate to another flotation treatment (or cleaning operation) with or without an additional amount of oil, and the tailings from this cleaning operation is the zinc middling product set forth in the preceding tabulation.

follows. It is well known that the cyanides are exceedingly active, chemically. By

Per Assays Percentrecovery- 3. A charge of ore ground through 65 Product. ff, mesh was. agitated in a flotatlon cell with an Fe Pb Fe Zn Pb equal welght of water for two mlnutes at a temperature of 180 F. wlth five pounds of P. ct. P.ct. P.ct. Heads ..100.0 8.0 15.0 7.0 10001000 100.0 lQ fi ic one l fl l of 1 Lead concentrate..... 10.0 2.0 7.5 56.0 2.5 5.0 80.0 lum cyanl per on O e ore Pu p Tailings 00.0 as? 15.6 1.55 01.5 95.0 20.0 was then diluted to 80% of water and oil Tot-aim; ..100.0 ..100.0 100.0 100.0 added, and the copper and lead concentrate removed.

per Assay. Per cent recovery. Product.

total. C11 Ag Fe Pb Cu Ag Fe Pb P ct. Oz. P. a. P. a. Heads 100 0 l. 54 14. O 17. 6 4. 66 100. 0 100. 0 100. O 100. 0

Lead concentrate 23.6 6.90 64.6 14.3 19.30 95.5 98.3 17.3 98.2 Tailings 70.4 0.09 0.3 18.5 Tr. 4.5 1.1 82.7 1.8

Total 100.0 100.0 100.0 100.0 100.0

treating the ore pulp with an alkali, alkali earth or metallic cyanide, as hereinbefore described, we find that the lead sulfide is actually cleaned and made more amenable to flotation. Any lead thiocyanate resulting from this cleaning action is readily soluble in the electrolyte used, that is, in the the recovery in the subsequent flotation treatment of the major portion of the lead sulfide present in the ore The action of the c-yanides upon the zinc sulfide appears to be to deaden the zinc sulfide by coating the particles thereof with a very thin film of zinc cyanide or complex cyanides formed by the action of the cyanides upon the sulfides of iron. The iron sulfides appear alsoto be coated by these complex cyanides whichare combinations of the ferro and ferri salts. The alkaline salts, which are used in accordance with our invention in combination with the cyanide, tend to convert the coating of the iron sulfide particles to the hydrated oxide of iron, and we find that at no stage of the process is the iron sulfide easily floated.

The caustic soda, or other appropriate find that sodium bicarbonategives better results, that is, results in a better separation of the lead from the zinc, because it (sodium bicarbonate) is less basic than sodium carbonate.

The ore itself, dependent upon the nature of its gangue and sulfides, exerts a considerable influence upon the operation and results of the process. In the treatment of various types of complex ores, the procedure is somewhat varied according to'the character of the ore. 'VVe have found, however, in every instance that the general conditions hereinbe-fore described are essential if satisfactory results are to be obtained.

Zinc sulfate is employed in order to prevent the zinc sulfide in the ore from floating with and contaminating the lead product. Its probable function is to remove the hydroxyl ion by combining with it, otherwise the hydroxyl ion will: dissolve the film upon the zinc sulfide and allow the zinc sulfide to float with the lead sulfide. The zinc sulfate may enter into combination with the cyanides formed and furnish additional Zinc for the production of the complex cyanides which perhaps, are not so soluble as the simpler cyanides.

We find that with some ores only sodium carbonate (or equivalent alkali salt) and so dium cyanide (or equivalent cyanide) are necessary; while with other ores sodium b1- carbonate (or equivalent alkaline salt) and sodium cyanide (or equivalent cyanide) are required; and with some ores the best results are secured by the combination of either sodium carbonate or sodium bicarbonate (or equivalent alkaline salt), sodium cyanide (or equlvalent cyanide) and zinc sulfate (or equivalent salt).

From the foregoing description and examples, it will be evident to those skilled in the art that the method of our invention provldes an effective procedure for selectively recovering galena by flotation from a mixed or complex ore containing zinc sulfide and (or) iron sulfide associated with the lead sulfide. If the ore contains any copper or silver sulfide, such sulfides will becarried into the lead concentrate. By the treatment of such a mixed or complex sulfide ore with a cyanide and an alkaline salt, the flotation of the lead sulfide is permitted and the flotation of any, iron or zinc sulfide is substantially inhibited. After the recovery of the lead concentrate, the zinc sulfide in the remaining ore pulp can be readily rendered amenable to flptatio-n by treating such remaining ore pulp with caustic soda, and in the subsequent flotation treatment the. zinc sulfide is selectively removed from the ore pulp,

leaving substantially all of the iron sulfide in the tailings, from whence the iron sulfide may, if desired, be removed by a subsequent flotation operation.

Gyanides are more active in neutral than in alkaline p-ulps, and for this reason, we

have, in some cases, improved our results b treating the ore pulp with cyanide, or wit cyanide and zinc sulfate, previous to the addition to the ore pulp of the alkaline carbonate.

We have also found, in certain cases, that when sodium cyanide and sodium carbonate are used together, no additional reagent (save more oil) is required to float the zinc sulfide. In other words, the use of caustic soda to float. the zinc sulfide is sometimes unnecessary. y

We do not wish to confine ourselves to any certain temperature or range of temperatures, since both the preliminary treatment and the sub-sequent flotation operations may be conducted in the cold. Pulp having a low temperature will require a longer reliminary treatment, than that at a higher temperature. However, our best results have been obtained when using a temperature of about 120 F., or more, in the preliminary treatment, but the pulp temperatures in both the first and second flotation operations may be any temperature which the. addition of the necessary amount of cold water will produce. a

Our invention is applicable to ores, concentrates, tailings and other metallurgical products, for which the term ores is used ing the thus treated ore to a flotation opera-- tion whereby the lead sulfide 1s 1n large part. recovered in the resulting froth and the flotation of the iron sulfide is in large part inhibited.

2. A process of concentrating by flotation an ore containing lead sulfide and zinc sulfide which comprises treating the ore with a cyanide and an alkaline salt, and subjecting the so treated ore to a flotation operation whereby the lead sulfide in the ore is in large part recovered in the resulting overflow froth and the flotation of the zinc sulfide in the ore is in large part inhibited.

3. A process of concentrating b flotation an ore containing lead sulfide, zinc sulfide and iron sulfide, which comprises treating the ore with a cyanide and an alkaline salt, and subjecting the so treated ore to a flotation operation whereby the lead sulfide in the ore is in large partrecovered in the resulting overflow froth and the flotation ofthe zinc sulfide and the iron sulfide in the ore is in large part inhibited. V

4. process of concentrating by flotation an ore containing lead sulfide and iron sulfide which comprlses treating the ore with a cyanide and an alkaline salt, and subjecting the so treated ore to a flotation operation and thereby effecting the recovery of the lead sulfide in the resulting overflow froth and inhibiting the flotation of the iron sulfide.

5. A process of concentrating by flotation .an ore containing lead .sulfide and one or more metallic sulfides including iron sulfide which comprises subjecting the ore in the form of an ore pulp and heated to a temperature above 120 F.'to the action of a cyanide and an alkaline salt, and subjecting the so treated ore pulp to a flotation operation whereby the lead sulfide is in large part recovered in the resulting froth and the flotation of the iron sulfide is in large part inhibited.

6. A process of concentrating by flotation an ore containing lead sulfide and one or more other metallic sulfidesincluding zinc sulfide which comprises subjecting the ore in the form of an ore .pulp and heated to a temperature above 120 F. to the action of a cyanide and a soluble carbonate, and subjecting the so treated ore pulp to a flotation operation whereby the lead sulfide is in large part recovered in the resulting froth and the flotation of the zinc sulfide is in large part inhibited.

7. A process of concentrating by flotation part recovered in the resulting froth.

an orecontaining lead sulfide and one or in the form of an ore pulp to the action of an alkali cyanide and an alkali carbonate, and subjecting the so treated ore pulp to a flotation operation whereby the lead sulfide is in large part recovered in the resulting froth and the flotation of the zinc sulfide is in large part inhibited.

8. process of concentrating by flotation an ore containing lead sulfide and one or more other metallic sulfides including zinc sulfide which comprises subjecting the ore in the form of an ore pulp and at a temperature higher than 120 F. to the action of an alkali cyanide and an alkali carbonate, and subjecting the so treated ore pulp to a flotation operation whereby the lead sulfide is in large part recovered in the resulting froth and the flotation of the zinc sulfide is in large part inhibited.

9. A process of concentrating by flotation an ore containing lead sulfide and iron sulfide which comprises subjecting the ore in the form of an ore pulp to the action of a cyanide and a soluble carbonate, and subjecting the so treated ore pulp to a flotation operation and thereby recovering the lead sulfide in large part in the resulting overflow frothwhile the flotation of theiron sulfide is inhibited.

10. A process of concentrating by flotation an ore'containing lead sulfide and iron sulfide which comprises subjecting the ore in the form of an ore pulp and heated to a temperature above 120 F. to the action of an alkali cyanide and an alkali carbonate, and subjecting the so treated ore pulp to a flotation operation and' thereby effecting the flotation of the lead sulfide while inhibiting the flotation of the iron sulfide.

11. A process of concentrating by flotation an ore containing lead sulfide and zinc sulfide which comprises subjecting the ore in the 11 0 form of an ore pulp to the action of a cyanide, an alkaline salt and zinc sulfate, and subjecting the so treated ore pulp to a flotation operation and thereby effecting the flotation of the lead sulfide while inhibiting the flotation of the zinc sulfide.

12. The process of concentrating by flotation an ore containing lead sulfide and zinc sulfide which comprises subjecting the ore in the form of an ore pulp to the action of a cyanide and an alkaline salt, subjecting the so treated ore ulp to a flotation operation and thereby e ect'ing in large part the flotation of the lead sulfide while inhibiting in large part the flotation of the zinc sulfide, treating the remaining ore pulp with an alkali, and subjecting the so treated remaining ore pulp to another flotation operation whereby the zinc sulfide is in large 13. A process of concentrating by flotation an ore containing lead sulfide and zinc sulfide which comprises subjecting the ore in the form of an ore pulp and heated to a temperature higher than 120 F. to the action of a cyanide and a soluble carbonate, subjecting the so treated ore pulp to a flotation operation and thereby effecting the flotation of the lead sulfide while inhibiting the flotation of the zinc sulfide, treating the remaining ore pulp with an alkali, and subjecting the thus treated remaining ore pulp to a flotation operation and thereby effecting the flotation of the zinc sulfide.

14. A process of concentrating by flotation an ore containing lead sulfide and zinc sulfide which comprises subjecting the ore in the form of an ore pulp to the action of a cyanide, an alkaline salt and zinc sulfate, and subjecting the so treated ore pulp to a flotation operation and thereby efiecting in large part the flotation of the lead sulfide and inhibiting in large part the flotation of the zinc. sulfide, treating the remaining ore pulp with an alkali, and subjecting the so treated remaining ore pulp to another flota tion operation whereby the zinc sulfide is in large part recovered in the resulting froth.

15. A process of concentrating by flotation an ore containing lead sulfide and zinc sulfide which comprises subjecting the ore in the form of an ore pulp and at "a temperature above 120 F. to the action of a cyanide, a soluble carbonate and zinc sulfate, subjecting the so treated ore pulp to a flotation operation and thereby 'e ecting the flotation of the lead sulfide and inhibiting the flotation of the zinc sulfide, treating the remaining ore pulp with an alkali, and subjecting the thus treated ore pulp to another flotation operation and thereby effecting the flotation of the zinc sulfide.

16. A process of concentrating by flotation an ore containing lead sulfide, zinc sulfide and iron sulfide Which comprises sub-' jecting the ore in the form of an ore pulp to the action of a cyanide, an alkaline salt and zinc sulfate, subjecting the so treated ore pulp to a flotation operation and thereby effecting in large part the flotation of the lead sulfide and inhibiting in large part the flotation of the zinc and non sulfides, treating the remaining ore pulp with an alkali, and subjecting the so treated remaining ore pulp to another flotation operation and thereby effecting the flotation of the zinc sulfide and inhibiting the flotation of the iron 17. A process of concentrating by flotation an ore containing lead sulfide, zinc sulfide and iron sulfide which comprises subjecting the ore in the form of an ore pulp and at a temperature above'120 F. to the action of a cyanide, a soluble carbonate and zinc sulfate, subjecting the so treated ore pulp to a flotation operation and thereby permitting the flotation of the lead sulfide and inhibiting the flotation of the zinc and iron sulfides, treating the remaining ore pulp with an. alkali, and subjecting the thus treated remaining orepulp to another flotation operation and thereby effecting the flotation of the zinc sulfide and inhibiting the flotation of the iron sulfide.

18. A process for effecting a differential flotation of lead sulfide and iron sulfide, which comprises subjecting an ore pulp containing such sulfides to a flotation operation in the presence of a cyanide and an alkaline salt and therebyeffecting the flotation of the lead sulfide and inhibiting the flotation of the iron sulfide.

19. A process for effecting a differential flotation of lead sulfide and zinc sulfide which comprises subjecting an ore pulp containing such sulfides to a flotation operation in the presence of a cyanide and an alkaline salt and thereby effectin the flotation of the lead sulfide and inhibiting the flotation of the zinc sulfide.

20. A process for effecting a differential flotation of lead sulfide, zinc sulfide and iron sulfide which comprises subjecting an ore pulp containing such sulfides to a flotation operation in the presence of a c anide and an alkaline salt and thereby e ecting the flotation of the lead sulfide and inhibiting the flotation of the zinc and iron sulfides. j

'21. A process for effecting a differential flotation of lead sulfide and one or more metallic sulfides, which comprises subjecting an ore pulp containing such sulfides to a flotation operation in the presence of a cyanide and a soluble carbonate and there by effecting the selective flotation of the lead sulfide.

In testimony whereof we a-flix our signatures.

GUY E. SHERIDAN. GEO. G. GRISVVOLD, JR. 

